RIYADH—Barack Obama's visit to Saudi Arabia on Friday marks a bid to warm relations that the Saudis hope will result in commitments by the U.S. president to boost the supply of sophisticated weapons to Syrian insurgents.

Mr. Obama's stopover at the end of a European tour will mark his first visit to the kingdom since U.S.-Saudi ties were severely strained last year following the renewal of high-level U.S. contacts with Iran and the...